RIPARIAN AREA MANAGEMENT
TR 1737-10 1994, Revised 2001
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U.S. DEPARTMENT OF THE INTERIOR
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BUREAU OF LAND MANAGEMENT
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U.S. Department of the Interior
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The Use of Aerial Photography
to Manage Riparian-Wetland Areas
Bureau of Land Management
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TR 1737-10
BLM/ST/ST-01/002+1737
(formerly BLM/SC/ST-94/005+1737)
RIPARIAN AREA MANAGEMENT
The Use of Aerial Photography
to Manage Riparian-Wetland Areas
by
Pam Clemmer
Cartographer/Remote Sensing
Bureau of Land Management
National Science and Technology Center
Denver, Colorado
Technical Reference 1737-10
1994, Revised 2001
U.S. Department of the Interior
Bureau of Land Management
National Science and Technology Center
P.O. Box 25047
Denver, CO 80225-0047
i
Suggested citations:
Clemmer, Pam. 1994, Revised 2001. Riparian area management: The use of aerial
photography to manage riparian-wetland areas. Technical Reference 1737-10.
Bureau of Land Management, Denver, CO. BLM/ST/ST-01/002+1737. 54 pp.
U.S. Department of the Interior. 1994, Revised 2001. Riparian area management: The
use of aerial photography to manage riparian-wetland areas. Technical Reference
1737-10. Bureau of Land Management, Denver, CO. BLM/ST/ST-01/002+1737. 54 pp.
ii
Acknowledgments
This is an enhanced version of Technical Reference 1737-2, The Use of Aerial
Photography to Inventory and Monitor Riparian Areas (Batson et al. 1987). Although
much of the original content remains, this revised reference approaches the topic from
a broader perspective.
The author wishes to thank the following individuals from the BLM Service Center
(now the National Science and Technology Center) for the time they offered in review,
comment, and development of this document: Don Prichard, Alan Amen, Larry
Cunningham, and especially Ed Work.
A special thanks to Jason Swegle of the Remote Sensing Staff and to Linda Hill and
Janine Koselak of the Technology Transfer Staff at the BLM Service Center (now the
National Science and Technology Center) for making this a quality document.
iii
iv
Table of Contents
Page
I.
Introduction ........................................................................................................ 1
II. Purpose ............................................................................................................... 3
III. Acquiring Aerial Photography ........................................................................... 5
A. Planning the Project .................................................................................... 5
B.
1.
Choosing Photo Parameters ................................................................ 5
2.
Researching Existing Photos ............................................................... 7
Contracting for Aerial Photography ......................................................... 10
1.
Planning for an Aerial Contract ......................................................... 11
2.
Initiating an Aerial Contract .............................................................. 13
3.
Placing Ground Targets ..................................................................... 14
4.
Collecting Data On-Site .................................................................... 15
IV. Interpreting and Analyzing Aerial Photos ........................................................ 17
A. Involving Others in Analysis .................................................................... 17
B.
C.
1.
Using Local BLM Staff ..................................................................... 17
2.
Requesting Service Center Assistance .............................................. 17
3.
Contracting for Analysis ................................................................... 17
Initiating Interpretation ............................................................................. 17
1.
Preparing the Photos ......................................................................... 18
2.
Selecting the Minimum Mapping Unit (MMU) ................................ 19
3.
Developing the Vegetation Analysis Framework .............................. 20
4.
Analyzing the Photos ........................................................................ 20
5.
Using Photo Mensuration .................................................................. 21
Capturing Data for GIS Input ................................................................... 22
1.
Determining the Map Base ................................................................ 22
2.
Transferring Data to the Map Base ................................................... 22
3.
Capturing Data in a GIS .................................................................... 23
v
V.
Using Remote Sensing for Field Applications ............................................... 25
A. Inventorying and Monitoring Riparian-Wetland Areas........................... 25
1.
Acquiring Photos for Monitoring .................................................... 26
2.
Analyzing Photos for Monitoring .................................................... 26
B. Determining Classification ..................................................................... 26
C. Assessing Functionality .......................................................................... 27
D. Supporting Other Management Techniques ............................................ 28
VI. Summary ......................................................................................................... 31
Literature Cited ........................................................................................................ 33
Appendix A: Minimum Mapping Unit Templates ................................................ 35
Appendix B: Sample Vegetation Analysis Framework ......................................... 39
Appendix C: Remote Sensing Application Guide for Riparian-Wetland
Area Management............................................................................ 41
Appendix D: Aerial Photo Samples ...................................................................... 47
vi
The Use of Aerial Photography
to Manage Riparian-Wetland Areas
I. Introduction
Under the Federal Land Policy and Management Act (FLPMA) of 1976, the Bureau
of Land Management (BLM) is required to inventory lands and resources on a continuing basis. Aerial photography and other remote sensing techniques can be used to
obtain inventory data and can be valuable tools for making management decisions.
Aerial photos have proven especially useful in the management of riparian-wetland
areas.
There are many benefits to using aerial photography for managing riparian-wetland
areas. For example, using large-scale color infrared or natural color aerial photography can accelerate and enhance collection of ground data. Percent of canopy and
ground cover, bare soil, and acreage can also be calculated from aerial photos. Riparianwetland plant communities can be delineated for mapping purposes, and generalized
vegetation/soil correlations can also be made. Aerial photos furnish a historical
record of the condition of an area at a given point in time; therefore, changes in
riparian-wetland areas can be visually assessed by comparing aerial photos taken at a
later date. Aerial photos also link data geographically, allowing detailed vegetation
maps to be transferred to a Geographic Information System (GIS) for spatial modeling
purposes.
Remote sensing techniques provide valuable information for both ecosystem-based
and site-specific riparian-wetland management decisions. As BLM moves toward
ecosystem-based management, resources will be managed across jurisdictional
boundaries on a global, regional, or watershed basis. Small-scale aerial photos (e.g.,
1:40,000) and satellite imagery can provide a broad ecosystem perspective of a
watershed. Specific problem areas or limiting factors in the management of a riparianwetland area can be identified through preliminary analysis. Once problem areas are
identified, larger scale imagery (e.g., 1:12,000, 1:6,000, or 1:4,800), acquired using an
aerial camera on board a low-flying aircraft, can be used to focus on site-specific
areas of interest.
Baseline data is required to effectively manage riparian-wetland areas. Aerial photo
baseline data, when carefully selected prior to a project, allows analysis of a large
area of interest, at a minimum cost, in less time per hectare than conventional on-theground methods (Keating 1993). Properly documented baseline data can support or
disprove management decisions.
1
2
II. Purpose
The purpose of this technical reference is to provide resource specialists with the
basic information, concepts, and procedures associated with using aerial photography
to establish baseline data for effective management of riparian-wetland areas. This
technical reference provides suggestions for the use of various scales of photography,
guidance for acquiring aerial photography, and general procedures for conducting a
vegetation inventory.
3
4
III. Acquiring Aerial Photography
Successful projects using aerial photography are carefully planned prior to initiation.
The ultimate objective of a project must be defined before aerial photos are acquired.
Once the objective is defined, the project can proceed to the next phases, which
include: choosing the correct photo parameters (i.e., scale, type of film), acquiring
the data, preparing the data, interpreting the data, analyzing the data, transferring the
data to an appropriate map base, and capturing the data in a GIS. Although the initial
effort is time-consuming, once the data is entered into a GIS, the resource specialist
has developed a baseline that can be used for modeling analysis with other data sets.
State Office or National Science and Technology Center personnel are available to
lend technical assistance as needed.
A. Planning the Project
Planning for photo acquisition and analysis is a critical phase of the interpretive
effort that is often overlooked or ignored. First, and most importantly, the intended use of the resulting photography must be clearly defined prior to selection
and acquisition of the photography. Careful planning ensures that the correct
photo parameters (i.e., scale of photos, film type) are selected to accomplish the
task.
1. Choosing Photo Parameters
Remotely sensed data is most effective when used from a multistage perspective, which involves studying the overall area or ecosystem with satellite
imagery, or small-scale aerial photography, gradually focusing in on the sitespecific areas of interest with larger scale photography. Standard 7 1/2minute-scale topographic maps should be used in conjunction with satellite
imagery or small-scale (1:40,000 to 1:80,000) photos to delineate and determine overall condition of the watershed or limiting factors that help define
capability and potential. Once a broad overall perspective is acquired, riparianwetland areas in need of further study can be identified. Scale and film type
are selected based on the desired result. For example, after studying the
watershed using 1:40,000-scale photos, the resource specialist might want a
more intensive inventory over the project area at scales of 1:12,000, 1:6,000,
or larger.
a. Selecting Film
Resource specialists should determine the ultimate objective of their study
and select the scale and film type accordingly. If vegetation composition
is needed, color infrared photography should be chosen. Infrared film
allows the interpreter to detect subtle differences in vegetation due to
high sensitivity of the film in the infrared portion of the electromagnetic
spectrum. The human eye is not capable of discerning the infrared portion
5
of the electromagnetic spectrum. Advances in film technology allow us to
“see” a part of the spectrum that we do not see with our naked eye. Natural color film is adequate if more general information is desired, such as
acreage, percent of canopy cover, channel widths, stream lengths, general
improvement, or increase of riparian-wetland vegetation. Photos 1a and
2a in Appendix D provide a comparison of natural color and color infrared, respectively.
b. Selecting Scale
Resource specialists should determine the smallest scale possible to
accomplish the task. The concept of large scale versus small scale is often
confusing. When comparing a large- and small-scale photo over the same
site, features on the small-scale photo appear smaller. The representative
fraction (RF) scale is a small fractional number. For example, 1/24,000 is
a smaller scale than 1/12,000. These fractional scales are commonly
expressed as ratio scales of 1:24,000 and 1:12,000. If the film format is
the same for both photos (e.g., 9- x 9-inch), the small-scale photo (1:24,000)
covers a greater ground area than the large-scale photo (1:12,000).
Relatively speaking, a smaller scale requires fewer photos and covers a
larger area (Table 1). The interpretive process is accelerated because there
are fewer photos to interpret and transfer to a map base. With the proper
optical equipment, interpretation can be accomplished at a much smaller
scale (Aldrich 1979).
Care should be taken to select a scale that is small enough to make the job
easier, but large enough to interpret the detail needed. (Photos 2a and 3a
in Appendix D provide a comparison of different scales of the same area.)
As a test, several different scales of film transparencies or prints can be
ordered for the area of interest, such as stereo pairs at scales of 1:40,000
and 1:24,000, and larger scales of 1:12,000, 1:6,000, or 1:4,800. (Photos
5, 6a, and 7 in Appendix D are examples of larger scales.) The photos can
then be carefully studied and compared to determine the level of detail
derived from each. A smaller scale should be selected for synoptic coverage
and a larger scale for site-specific analysis.
6
Table 1. Estimating Photo Coverage per 100,000 Acres Based on Scale 1
Photo
scale
Number acres
per square
inch
Number acres
per photo 2
(3.6 by 6.3 inches)
Number photos
per
100,000 acres
1:2,400
1
23
4,348
1:4,800
4
91
1,099
1:6,000
6
136
735
1:12,000
23
522
192
1:15,840
40
907
110
1:20,000
64
1,452
69
1:24,000
92
2,087
48
1:40,000
255
5,783
17
1
Aldrich, Robert C., 1979. Remote Sensing of Wildland Resources: A State-of-the-Art Review,
General Technical Report RM-71; Table 4, p. 33.
2
60% overlap; 30% sidelap.
2. Researching Existing Photos
Before a new aerial contract is initiated, research should be done to determine whether
photos for the area of interest already exist. Photos are accessible from several sources.
a. National High Altitude Photography (NHAP)
The NHAP program acquired photos from 1979 to 1987. This photography
was funded by several Federal agencies and includes coverage of the lower
48 States in color infrared at 1:58,000 scale and in black and white at
1:80,000 scale. Although older, these photos provide excellent resolution
and historical perspective. The scale of the photos is appropriate for synoptic
viewing of an area, watershed delineation, general riparian-wetland analysis,
and change detection applications. The U.S. Forest Service produced
several case studies that use NHAP for riparian-wetland inventory applications (Mereszczak et al. 1990). U.S. Fish and Wildlife Service has used
1:58,000 color infrared NHAP for wetlands delineation.
b. National Aerial Photography Program (NAPP)
NAPP replaced the NHAP program in 1987. Funded by the same agencies,
NAPP provides complete cyclic coverage of the lower 48 States beginning
in 1987. NAPP photos were originally obtained using color infrared film
at a scale of 1:40,000 (Photo 3a, Appendix D). Coverage is available for
nearly all the Western States. Due to national mapping requirements for
the Digital Orthophotography Quadrangle (DOQ) program, NAPP now uses
black-and-white film almost exclusively. Black-and-white film provides
7
higher resolution needed for orthophoto production at lower cost than
color infrared film. The scale of the NAPP photos (1:40,000) is appropriate
for the same applications as those listed for NHAP. Both NHAP and
NAPP provide high-quality photographic products that can be satisfactorily
enlarged to 1:24,000 scale. Photos 3a and 4 in Appendix D provide a
comparison of these scales. Anderson and Hardin (1992) have demonstrated
the use of NAPP color infrared photos for delineating wetlands in Utah.
NHAP and NAPP photography can be aquired from EROS Data Center (EDC)
in Sioux Falls, South Dakota, or the U.S. Department of Agriculture's Aerial
Photographic Field Office (APFO) in Salt Lake City, Utah. Online searches
and ordering can be conducted at http://edcsns17.cr.usgs.gov/EarthExplorer/.
c. BLM Photography
BLM has acquired a considerable amount of aerial photography over the
years. Most of this photography is archived at BLM's Aerial Photography
Archive and Processing Lab, Denver Federal Center, CO 80225, with the
remainder stored at EDC. BLM photos consist of resource block photography
at scales from 1:12,000 to 1:24,000. Block photography implies photography
acquired as adjacent photo flight lines. Block photography usually has 60
percent endlap between successive photos with a sidelap between adjacent
flight lines of 30 percent. Smaller scales (e.g., 1:24,000) are appropriate for a
broad perspective of a stream reach and generalized riparian-wetland analysis.
Smaller areas of strip photography (riparian-wetland and special projects)
are acquired in select areas at larger scales of 1:6,000, 1:4,800, or 1:3,000
(Photo 5, Appendix D). Strip photography consists of a single flight line
of photos (e.g., stream reaches) where an endlap between successive
photos of 60 percent is commonly maintained for purposes of stereoscopic
viewing. Site-specific riparian-wetland inventory is easily accomplished
at scales of 1:12,000, 1:6,000, or greater. If vegetation differentiation is a
requirement, color infrared film is preferred over natural color.
d. Aerial Photography Summary Record System (APSRS)
The APSRS is a photography database maintained by the Earth Science
Information Center (ESIC) of the United States Geological Survey (USGS).
This record system lists photos available from various Federal, State, and
local governments, and from private companies that maintain aerial
photography film archives. NHAP, NAPP, and BLM photos are found in
this listing, in addition to photos from many other sources. The listing is
referenced by the geographic coordinate (latitude/longitude) of the southeast
corner of any 7 1/2-minute topographic map. BLM's National Science and
Technology Center (NSTC) staff can supply a microfiche listing from the
database for any specified topographic map upon request. The APSRS
database is also available on CD-ROM from the USGS for a nominal
cost. Figure 1 shows a sample of the APSRS listing for the Palmer Lake
7 1/2-minute quadrangle.
8
Figure 1. Palmer Lake, Colorado (39° 00' N, 104° 52' W), APSRS listing.
9
If aerial photos for the area of interest already exist, adequate time should be
allowed to order and receive the prints or film. In many instances, it can take
up to 8 weeks to receive photos. State Office remote sensing coordinators or
BLM's Aerial Photography Archive and Processing Lab can provide assistance
in obtaining photos from any of these sources.
Once the photos are received, resource specialists are ready for interpretation
and analysis. It is highly recommended that film transparencies be used
instead of prints. When viewed with adequate back-lighting, transparencies
provide sharper images, making interpretation easier. Of course, the stereoscopic equipment available to the interpreter determines whether film or prints
are ordered.
B. Contracting for Aerial Photography
If larger scale, more current aerial photos are desired, or if no photos exist for the
area of interest, an aerial photo contract should be considered. The following
contract guidelines are aimed primarily toward large-scale strip photography
contracts. Generally the same procedures apply for block photography acquisition. Tables 2 and 3 show approximate costs for both strip and block projects.
Table 2. Scale, Coverage, and Costs for Resource Block Aerial Photography Contracts
Approximate Cost
Per Square Mile ($)1
1
Scale
Descriptive
Scale
Color
Infrared
1:12,000
1" = 1,000'
36.00
42.00
1:15,840
= 1,320'
29.00
32.00
1:24,000
= 2,000'
12.00
14.00
Approximate costs are based on 1994 average contract costs. Actual cost may vary significantly
depending upon the region and size of the job.
Table 3. Scale, Coverage, and Costs for Strip (i.e., riparian) Aerial Photography Contracts
Approximate Cost
Per Linear Mile ($)1
Scale
Descriptive
Scale
Color
Infrared
1:2,400
1" = 200'
200.00
225.00
1:4,800
= 400'
175.00
200.00
1:6,000
= 500'
150.00
175.00
= 1,000'
100.00
125.00
1:12,000
1
Approximate costs are based on 1994 average contract costs. Actual cost may vary significantly
depending upon the region and size of the job.
10
1. Planning for an Aerial Contract
It is strongly recommended that resource specialists consult the State Office remote
sensing coordinators or NSTC remote sensing staff before initiating an aerial contract.
a. Selecting the Riparian-Wetland Area
Areas that are of primary concern should be selected carefully. The
beginning and end points of stream reaches requiring coverage should be
identified on a 1:24,000-scale USGS 7 1/2-minute topographic map
(Figure 2). It is best not to skimp on photo coverage. Once the aircraft is
over the area, an additional two or three exposures do not add significantly
to the overall cost of the project.
b. Determining Season and Time of Day
Ideally, the photos should be obtained as near to “peak of green” as possible.
This is generally near the point where vegetation is growing vigorously
and is at a full leaf stage. Local resource specialists usually know when
peak of green occurs. In addition, if deep canyons are in the area, field
specialists should specify a higher sun angle than normal (i.e., time of day)
for the flight in order to minimize shadows within the canyon depression.
The objective of the project should be considered when selecting the date
of photography. Generally, riparian vegetation is more easily distinguished
from upland vegetation in photos taken later in the growing season.
c. Selecting Film
The intended use of the imagery directly relates to the type of film required.
For example, if the extent of a riparian-wetland area is to be outlined and
quantified (in acres), natural color film is adequate. If vegetation composition (i.e., trees, shrubs, grasses) is to be analyzed, color infrared film is
preferred. Color infrared film captures a greater range of spectral reflectance
variation between vegetation types than does natural color film.
d. Selecting Scale
Intended use also has a direct bearing on scale requirements. For example,
a scale of 1:24,000 or smaller is sufficient to locate most riparian-wetland
areas, make linear (mileage) measurements, and determine watersheds.
However, to visually analyze, delineate, and measure areas to the community level for later comparison (monitoring), a scale of 1:2,400 to 1:6,000
is recommended for narrow strips of riparian-wetland vegetation. Wider
meandering riparian-wetland zones may require photo scales from 1:4,800
to 1:12,000 in order to photographically cover the area with a single flight
line. If the adjacent uplands are of interest, a smaller scale should be
considered. Again, the larger the scale, the more costly the project, so the
smallest possible scale for accomplishing the task should be selected.
11
Figure 2. Coverage required for Muddy Creek is identified on a USGS 7 1/2-minute topographic map.
12
2. Initiating an Aerial Contract
The necessary paperwork for an aerial contract should be initiated at least 6
months prior to the expected flight date to allow time for preparing specifications, requesting photo lab work, securing bids, awarding the contract, and
holding a prework conference. Contracts under $100,000 can be handled by
the State or Field Offices. Contracts of $100,000 or greater are handled by the
procurement staff at BLM's National Business Center.
a. Preparing Specifications for Aerial Photography
Technical aerial photography specification packets are available from
NSTC's aerial photo coordinator. These specifications incorporate the
preplanning considerations mentioned, in addition to other requirements
for obtaining quality imagery. Form 9672-3, Specification Detail Sheet
(July 1984), is an attachment to the specifications. The form provides
space for specific information relative to the acquisition of the photography and any additional requirements not covered in the specifications.
NSTC can provide these packets or assist in completing this form.
b. Preparing the Flight Map
Flight maps should be prepared from USGS topographic maps. The
1:24,000-scale, 7 1/2-minute topographic map is used for large-scale strip
projects (i.e., riparian) and the 1:100,000-scale map is used for smaller
scale block projects (e.g., 1:12,000, 1:24,000). Generally these maps are
prepared by the State Office remote sensing coordinators or the NSTC
aerial photo coordinator in consultation with the State or Field Office.
c. Procuring the Photography
The procurement process is usually handled by State Offices or NSTC.
Technical assistance on photo procurement procedures is available from the
NSTC aerial photo coordinator. The method of contracting for photography
is usually determined by the estimated size and cost of a project.
Cooperative planning between BLM offices and other Federal, State, and
local agencies can significantly reduce project costs. A major cost item is
ferry time for the flight crew from the contractor’s home base to the
project site. If the project is combined with another project in a nearby
area, the ferry charge is minimized.
Assuming the project cost is within the authority of the local contracting
officer, the following options for contracting the job are available:
1) A formal Invitation for Bid can be issued. This is done through the
National Business Center when large contracts are involved.
13
2) Standard Form 18 can be used to obtain written quotations. Under this
procedure, specifications, maps, and other items that clarify the request
for price quotations can be sent. At least 3 weeks should be allowed to
receive bids.
3) The Oral Quotations Form 1510-42 for supplies and services can be
used. This form is generally used for small aerial photo contracts with
requirements that can be described sufficiently over the phone to
obtain price quotes.
Any questions regarding the procurement process should be directed to
NSTC's aerial photo coordinator.
3. Placing Ground Targets
Ground targeting, also called paneling, is essential for larger scale photo contracts (i.e., 1:2,400 to 1:12,000). With larger scale photos, it is often difficult to
determine the photo scale using map identifiable features. Acquiring the known
ground distance between two targets allows the interpreter to calculate the
actual photo scale (Photo 6a, Appendix D). Once the photo scale is determined,
photo mensuration (linear measurements and acreage determination) can be
accomplished directly on the photo using a simple formula (see section IV.B.5).
Targeting should be completed not more than 1 week prior to flying to avoid
target loss from wind, animal disturbance, or vandalism. Target panels can be
constructed from butcher paper, which is readily available from butcher shops
and grocery stores, or from plastic material. Butcher paper is biodegradable,
but the plastic material is not. Targets should be anchored with twine, rocks,
or nails and large washers. The target material should be removed once the
aerial photography has been accepted. Sometimes photos from portions of
contracted flights are rejected due to clouds or excessive tip, tilt, or crab of the
aircraft, and those areas are required to be reflown.
For riparian areas along stream corridors, two targets should be placed at each
end of a stream reach. For longer stream segments, another set (two targets)
should be placed at approximately 2-mile intervals along the stream or at the
midpoint of the segment. The following guidelines are acceptable for photo
scales of 1:2,400 to 1:6,000:
14
•
Targets should be placed 200 to 500 feet apart within the photo coverage
area, with one of the targets near the stream where ground data and photos
will be taken. An accurate ground distance between the targets should be
measured and recorded for later use in determining photo scale. Targets
should be placed in relatively flat terrain within clear view of the aircraft.
•
Target panels should be in the form of crosses (+). Each target panel
should be 10 feet long and at least 18 inches wide for large-scale projects.
If photogrammetric work is anticipated, the requirements for target placement
are more strict. Horizontal and vertical control points need to be collected
using survey quality Global Positioning System (GPS) units. Photogrammetry
techniques are used to obtain extremely accurate measurements. NSTC's
photogrammetry staff should be consulted on target placement and is available
to assist in mission planning upon request.
4. Collecting Data On-Site
On-site data collection efforts should be accomplished at the time of target
placement. Data collected on-site provides the interpreter with valuable
information about on-ground conditions at the time the photos are acquired.
Photos 1b, 2b, and 3b of Appendix D show on-ground conditions for the areas
in Photos 1a, 2a, and 3a, respectively. Although field verification is valuable
anytime during the project, it is important for the interpreter to know the site
conditions at the time of photo acquisition.
Slides (35-mm) of the riparian-wetland area should be taken at the site where
the targets are placed, and inventory data should be collected for the reach.
The dominant and subdominant herbaceous vegetation, shrubs, and trees, and
the percent bare soil should be determined. Data acquired in the field can be
used to develop interpretive guidance once the photos have been acquired.
This data should include any additional field notes that may assist in photo
interpretation. Sketched maps annotated to indicate the presence and type of
land cover (e.g., plant species, soil type) are useful for developing photo
interpretation keys.
The approximate coordinate locations of the targets should be determined
from a topographic map (Photo 6a and 6b, Appendix D). Coordinate location
can be useful for locating oneself during interpretation. If possible, differentially corrected GPS coordinates for the center of the target panels should be
collected. Accurate coordinate locations aid in registering and entering data
into a GIS.
15
16
IV. Interpreting and Analyzing Aerial Photos
Once photos have been acquired, local BLM staff, State or NSTC personnel, or
contracted facilities can perform interpretation; however, interpretation is best performed by someone familiar with the local vegetation and ecosystem characteristics.
A. Involving Others in Analysis
1. Using Local BLM Staff
Photo interpretation and data analysis should be performed at the local Field
Office level by resource specialists familiar with vegetation and management
activities on the site. Interdisciplinary involvement in interpretive analysis
will provide a broader perspective. State and Field Office remote sensing
expertise should also be called upon, when available. Contacts should be
made with any Federal, State, and local agencies who may have an interest in
the area under consideration. These contacts may contribute expertise in
analysis, existing data, or financial assistance for a data-sharing project.
2. Requesting NSTC Assistance
Optical photo interpretation equipment is sensitive, fragile, and difficult to
move. Such interpretation equipment is available at the NSTC for use by
BLM Field Office personnel. Facilities and staff from the NSTC remote
sensing staff are also available to help field personnel with analysis. Generalized
interpretation can be accomplished at NSTC, followed by verification
assistance from specialists in the field.
3. Contracting for Analysis
Educational institutions, consulting firms, and other Government agencies
may offer interpretation and analysis capabilities. For instance, the Environmental Protection Agency (EPA) facility in Las Vegas, Nevada, has cooperated with BLM offices in past years. This type of cooperation varies from
performing the analysis and documenting the results to simply making their
facilities available for a BLM work session.
B. Initiating Interpretation
Input into a GIS requires transferring interpretations from aerial photos to a stable
map base. If GIS input is not the ultimate goal, and information is to be used
only to calculate approximate acreage of riparian-wetland vegetation, photo
mensuration procedures should be used (see section IV.B.5).
17
1. Preparing the Photos
a. Delimiting the Effective Area
During the interpretation process it is important to analyze only the
"effective area" of each photo. Generally, the effective area is the central
portion of the photo and includes overlap and sidelap from adjacent photos
(Figure 3). The effective area serves two purposes. It defines the area of
least geometric distortion in the photo and it allows the interpreter to
delineate and classify the features in a project area once and only once,
eliminating inefficient and multiple interpretations that could occur if a
larger area on the overlapping photo were to be interpreted. The drawing
of the effective area on every photo can be a tedious and protracted process, a discussion of which is beyond the scope of this technical reference.
Crisco (1988) provides detailed information regarding effective area
delineation.
Line of flight
1-3-9
1-3-8
Effective area of
photo 1-3-8 and 1-3-9
60% overlap
Figure 3. Effective area.
b. Preparing Overlays
Interpretations should be compiled on clear mylar overlays, thus allowing
the photos to be preserved for other applications. A clear mylar overlay
(9-x 9-inch) should be attached to each frame to be interpreted, and a finepoint permanent marking pen should be used to carefully annotate each
side fiducial mark observed on the photo. The identification format (photo
labeling) is then transferred from each photo so that it can be easily
reregistered if the overlay becomes detached. The identification format
18
includes the date of the photography, agency, scale, project code, and
frame number (roll-flight-exposure number) as shown in Figure 4.
Identification
format
6-15-90
BLM 5 ID-90-CI
1-3-8
Fiducial mark
Figure 4. Sample identification format.
2. Selecting the Minimum Mapping Unit
A minimum mapping unit (MMU) should be selected prior to photo interpretation. The MMU serves as a guide for all future polygon delineation and
mapping. For example, a 1-acre MMU would be equivalent to a 0.1-inch
square at 1:24,000 scale. Although very small features and individual plants
are discernible on large-scale aerial photos, a reasonable mapping unit must be
selected. The interpreter must keep in mind that the delineations will be
reduced in size significantly when the data is transferred to the map base. To
assist in interpretation, a template depicting the MMU at the intended scale
should be constructed to use as a guide during interpretation. Sample MMU
templates are provided in Appendix A.
Larger riparian-wetland areas can be portrayed as polygons on a 1:24,000-scale
map base. However, the majority of BLM streams have riparian-wetland
communities that are quite small and cannot be portrayed with polygons at a
scale of 1:24,000. This complicates the use of detailed riparian-wetland data
within a GIS. Features that are too small to portray with an MMU as a polygon
at the final map scale can be compiled as line or point data. Line segments must
be described and defined. Appropriate attributes must be assigned to features
when they are input into a GIS. For example, a red line segment represents a
width of less than 100 feet. This information, along with line length and map
scale, determines line segment acreage. Spot symbols need to be defined in
terms of area. For example, spot symbols represent areas less than .5 acre. GIS
feature design and descriptions are discussed at length in Technical Reference
1737-7, Procedures for Ecological Site Inventory—With Special Reference to
Riparian-Wetland Sites (Leonard et al. 1992). These procedures are easily
adapted to any GIS input procedure, but should be defined prior to map transfer.
19
3. Developing a Vegetation Analysis Framework
If vegetation analysis is part of the defined project, a vegetation analysis
framework should be developed prior to interpretation. This framework
describes the characteristics of the dominant and mixed riparian-wetland
communities to be encountered and delineated. As interpretation proceeds,
the framework is modified as needed. Appendix B provides an example of a
vegetation analysis framework that was used in 1986 during a work session in
Nevada and found to be adequate for that environment. Resource specialists are
urged to review this framework and create their own based on local requirements.
The framework should include defined criteria for the classes that are selected.
The previously selected MMU should be used for interpretations. Delineations
should be confined to the riparian-wetland area and interpretation kept within
the effective area.
4. Analyzing the Photos
Each information layer should be compiled on a separate overlay. For example,
stream channels on recent photos often show much change from the older
7 1/2-minute topographic maps. Stream channels, therefore, are compiled on
one overlay to monitor stream channel movement, while vegetation interpretations are compiled on a separate overlay. Separating the data layers allows
ease in map transfer and subsequent digitization.
Photo interpreters should use the best available optical equipment during the
initial stages of the project. A zoom transfer scope allows interpretations to be
directly compiled from photo to map base. If this equipment is not available,
a two-step process is required. Stereoscopic viewing of prints is helpful,
particularly in determining relative heights of tree and shrub species. Aerial
photographs can be obtained as paper prints or positive film transparencies.
Although paper prints are commonly used in the field, it is strongly recommended
that film transparencies be used with adequate back lighting for interpretation
because they provide a finer resolution image. Visual analysis using
transparencies under stereo magnification has proven to be of great value.
While interpreting the photo, it is best to proceed from the dominant or purer
types of communities to the more difficult mixed communities. Using the
MMU template as a guide for polygon delineation, each vegetation type
should be systematically identified. To develop interpretive consistency, all of
one type should be delineated at the same time. Jumping around creates
confusion in interpretation. Photo 7 in Appendix D shows interpretations on a
portion of Tabor Creek, NV.
Use of supporting ground photography is encouraged, as are field visits. If
aerial photography was contracted, the ground data that was collected when
targeting was accomplished (see section III.B.4) should be used. Photo
interpretation is a confidence-building exercise and it is important to use all
20
available supporting data. Although the first several photos take longer,
experience has shown that photo interpreters increase their speed and efficiency
once confidence is gained.
When analysis is complete, interpretations can be transferred to a standard
map base. Once transfer is completed, the compilation can be entered into a
GIS. Once input into a GIS, future monitoring, change detection, and analysis
can be achieved quickly (see section IV.C).
If input into GIS is not required, and the dominant use of the data is to gather
tabular information concerning approximate acreage, photo mensuration is
possible.
5. Using Photo Mensuration
After the photo preparation and interpretation processes are complete, it is
possible to tabulate acreage directly from the photos. This process is called
photo mensuration. The resulting acreage figures are approximations; this
method is far less accurate due to the lack of a controlled map base. Photo
mensuration is more accurately calculated on interpretations that have been
carefully transferred to a map base.
a. Determining Photo Scale
The contracted photo scale, which is normally annotated in the identification format on each photo, is not the actual photo scale. When severe
elevation changes occur within any flight line, the actual photo scale
varies considerably and affects the mensuration results. The actual scale
on any given photo is calculated using a known ground distance. On
large-scale photos, this distance is obtained between the target sets that are
placed before the flight (see section III.B.3). On smaller scale photos,
calculation is commonly made by measuring a distance between two
photo- and map-identifiable features (Crisco, 1988). An average scale for
the flight line can then be determined for mensuration purposes.
Photo scale (PS) is the ratio of photo distance (PD) to ground distance
(GD). All values must be converted to the same unit of measure.
PD
= PS
GD
Example: The ground distance between targets A and B is 400 feet. The
photo distance between the same targets A and B is 2 inches. What is the
photo scale?
2" (PD)
2" (PD) – 2"
1"
=
=
400' x 12" (GD) 4,800" (GD) – 2"
2,400"
•
•
•
•
Photo Scale = 1:2,400
21
Photo scale is expressed as a ratio: 1 inch on the photo represents 2,400
inches on the ground. Once the photo scale is determined, the descriptive
scale is easily calculated. The descriptive scale shows how many feet on
the ground are equivalent to 1 inch on the photo. In this example, the
descriptive scale is figured as follows:
1"
1"
=
2,400" – 12"
200'
•
•
Descriptive Scale: 1"=200'
b. Calculating Acreage
There are several methods for determining acreage. These methods may
be used directly on the photo, but are more accurate if used on a controlled
map base once the interpretations have been transferred.
Many Field Offices have access to digital planimeters that allow direct
calculation of acreage when the photo scale is entered. Additionally,
portable digital planimeters can be rented on a daily basis at a reasonable
cost.
If the project area is small, the dot grid and manual methods are costefficient alternatives (Crisco 1988). Acreage calculation can be determined with most GIS software packages, once the interpretations are
digitized.
As the data is assembled, it should be recorded on a vegetation analysis
framework form (Appendix B). The data can be recorded by photo number, and subsequent tabulation by other subdivisions (e.g., allotment,
ownership, stream segment) is possible if desired.
C. Capturing Data for GIS Input
1. Determining the Map Base
If data is primarily to be used to create a map of riparian-wetland cover types
and may ultimately be used in a GIS, map base considerations are critical.
The standard base for BLM resource management applications is the USGS
7 1/2-minute, 1:24,000-scale topographic map or orthophoto quadrangle.
Stable base mylar provides the most accurate digitizing base and should
always be used in place of paper print products.
2. Transferring Data to the Map Base
Aerial photos contain displacement and distortion and do not provide map
accuracy for measuring purposes. Photo analysis should be followed by
transfer of the detail onto a map base to provide input for a GIS. This process
22
prevents duplication of effort in future monitoring and supports baseline data
acquisition for ecosystem-based management activities.
To begin map transfer, the vegetation analysis framework, the map base MMU
template (i.e., 1:24,000), and the GIS compilation guidelines discussed in
section IV.B.2 should be used. The interpretations from the photos should be
carefully compiled onto a stable base orthophoto. Detail is easier to transfer
from an aerial photo to an orthophoto because both have photo-identifiable
features in common. If orthophotos are not available, 7 1/2-minute topographic maps can be used as a base. Discrete boundaries of the lines and
polygons, along with appropriate labels, should be transferred to the base map.
If the finished compilation overlay is to be mechanically scanned, the compilation method for producing the most efficiently scanned overlay should first
be determined. For example, black lines with blue attribute labels are easier
to scan and edit than numerous color classes.
Once interpretations are transferred to the map base, the manual photo mensuration technique can be used to acquire acreage figures, which is more accurate
than direct mensuration off the photos. If the area is large and the desired
result is analysis in a GIS, alternate data capture methods are more efficient.
3. Capturing Data in a GIS
Once the data has been compiled on a stable map base, it is ready to enter into
a GIS. A local GIS specialist should be consulted to determine the most
efficient method of input. Manual digitizing on a tablet is commonly used.
Heads-up digitizing from a digital orthophoto is also a common method of
input. Scanner technology is popular, although it is somewhat costly. A drum
scanner is available for use at NSTC.
23
24
V.
Using Remote Sensing for Field Applications
Methods and standards for managing riparian-wetland areas have been established
within BLM’s technical reference series (TR 1737) on riparian area management.
Remote sensing techniques can be applied in virtually all types of riparian-wetland
management. Inventory and monitoring are more traditional uses of remotely sensed
data. However, aerial photography can also assist in assessing functionality, determining classification, and improving management planning processes. The table in
Appendix C provides suggestions on how to use remotely sensed data for riparianwetland management applications. Suggested scales and film types are also given.
Actual scale and film selection should be determined by the intended use and size of
the area. Resource specialists may find that other scales or film types are adequate
for their applications.
A. Inventorying and Monitoring Riparian-Wetland Areas
Remote sensing techniques have long been used to inventory and monitor riparianwetland areas. Using the appropriate date, scale, and film, riparian-wetland
vegetation can be interpreted and measured using methods described in section
IV. Small-scale photos give a general overall perspective of the area, including
the geomorphology, landform, drainage pattern, and watershed area and condition.
Aerial photos can be used to determine channel sinuosity, channel confinement,
and valley width, and provide a more accurate basis for analysis than topographic
maps. Stereoscopic photo interpretation, along with physiographic analysis of a
7 1/2-minute topographic map, allow preliminary ecological typing. Initial
assessment of vegetative bank protection and water sedimentation can be performed
using medium- or large-scale aerial photos. Vegetation association and phase can
be identified using aerial photos, as discussed in-depth in Technical Reference
1737-3, Inventory and Monitoring Riparian Areas, (Myers 1989). Certainly tree
canopy, herbaceous cover, and to some extent, age distribution of woody dominant
species can also be identified using aerial photos at an adequate scale.
Technical Reference 1737-8, Greenline Riparian-Wetland Monitoring (Cagney 1993),
discusses methods that can utilize large-scale (1:2,400) color infrared photography.
The Forest Service General Technical Report 47, Monitoring the Vegetation Resources
in Riparian Areas (Winward 2000), offers additional, updated information on this
topic. Recommended transect length is a minimum of 726 feet along the greenline.
At 1:2,400 scale, 1 inch on the aerial photo represents approximately 200 feet on
the ground. With color infrared film, vegetation composition can be differentiated
along the transect. In fact, resolution at that scale is better than 1 foot. After field
checks have been conducted, interpretations can be used to support the baseline data.
The most easily detected change in a riparian-wetland area is a reduction in foliar
cover and an increase in bare soil. This change may be obvious upon inspection
of the baseline (initial) photo compared with monitoring photos taken 5 to 10
years later. The cause of the change may be answered only by on-the-ground
inspection. The photos offer an opportunity to monitor the extent of change, but
not necessarily the cause.
25
Once baseline data is established, a monitoring plan should be initiated for those
areas in need of more intense scrutiny. Videography is especially well suited for
quick damage assessment, but resolution is much lower than conventional aerial
photography.
1. Acquiring Photos for Monitoring
The same considerations outlined for the original aerial photography contract
should be used to plan subsequent flights for monitoring purposes. Area
selection, season and time of day, film type, scale, specifications, procurement,
and ground targeting requirements should follow the same criteria as the
original project. Flight maps used in the previous project should be referred to
in designing the subsequent flights. The idea is to create conditions as close
to those of the previous flight as possible. Although not mandatory, using the
same conditions greatly simplifies interpretation.
2. Analyzing Photos for Monitoring
The old and new aerial photos over the riparian-wetland area, along with
smaller scale photos of the watershed, should be compared visually. From this
comparison, critical areas can be evaluated and apparent changes occurring on
nonstudy areas can also be detected and documented. One of the important
advantages of a photo-based monitoring system over entirely ground-based
study is the ability to expand the area that can be evaluated.
It is anticipated that several key areas will already be selected prior to having
the area reflown. These sites should be closely evaluated. Interpretation and
analysis should again be performed on these key areas and results compared.
It is important to remember that critical steps performed during the initial
baseline interpretation are essential for monitoring the areas. In addition, if
the visual comparison yielded further areas of change, a reinterpretation may
be appropriate. Once photo interpretation and analysis are complete, the
probable causes of change should be investigated.
B. Determining Classification
As with inventory and monitoring, remote sensing brings an added dimension to
the classification process, which is discussed in Technical Reference 1737-5,
Riparian and Wetland Classification Review (Gebhardt et al. 1990). Possibly the
greatest benefit is the overall perspective that is provided with smaller scale
imagery. Using a broad approach allows limiting factors in the landscape to
manifest themselves. Emphasis should be placed on using the remotely sensed
data as a prerequisite to the classification itself.
Technical Reference 1737-7, Procedures for Ecological Site Inventory—With Special
Reference to Riparian-Wetland Sites (Leonard et al. 1992), describes a process
that looks at the interaction between soils, climate, hydrology, and vegetation for
riparian-wetland resources and uplands. This highly interdisciplinary activity
26
lends itself well to using remote sensing techniques. Using appropriate imagery
of the area under study, each interdisciplinary team member can relate their
perspective of the study area. After initial team observations are made, individual
study can be undertaken to determine such things as vegetation composition and
acreage, canopy cover, bare soil, locations for gathering hydrologic information,
present vegetation as compared with previous historical photos, open water
surface area, soil and surface geology characteristics, and general watershed
quality.
C. Assessing Functionality
Considerable effort has been expended to inventory, classify, restore, enhance,
and protect riparian-wetland areas. The following technical references define a
structured interdisciplinary activity that assists resource specialists in determining
the condition of riparian-wetland areas on public lands:
TR 1737-9, Process for Assessing Proper Functioning Condition (Prichard et
al. 1993)
TR 1737-11, Process for Assessing Proper Functioning Condition for Lentic
Riparian-Wetland Areas (Prichard et al. 1994)
TR 1737-15, A User Guide to Assessing Proper Functioning Condition and
the Supporting Science for Lotic Areas (Prichard et al. 1998)
TR 1737-16, A User Guide to Assessing Proper Functioning Condition and
the Supporting Science for Lentic Areas (Prichard et al. 1999)
Although riparian-wetland areas are small in comparison to the vast acreage of
public lands, assessing the condition of all these areas is an extensive effort.
Aerial photos can assist in the initial planning for functionality assessment.
Remotely sensed data can be beneficial in determining existing condition, potential
condition, resource values, planned actions, and monitoring requirements.
Aerial photos can be used to assist in completing the reporting tables shown in
these technical references to define riparian-wetland management objectives.
Riverine miles, acreage, and preliminary determination of functioning condition
can be assessed using remotely sensed data. Initial trend can be assessed using
historical photos. Given the appropriate scale and film type, aerial photos can
significantly reduce field time and overall evaluation efforts.
Technical Reference 1737-12, Using Aerial Photographs to Assess Proper Functioning Condition of Riparian-Wetland Areas (Prichard et al. 1996), provides detailed
explanations and procedures for using aerial photography to assess condition.
27
D. Supporting Other Management Techniques
Grazing management, as discussed in Technical References 1737-4, Grazing
Management in Riparian Areas (Kinch 1989), and 1737-14, Grazing Management
for Riparian-Wetland Areas (Leonard et al. 1997) can be enhanced by using
remotely sensed data to develop alternative strategies. Using historical photos,
range conservationists are able to ascertain how management strategies used over
the years have impacted the land. Heavily grazed riparian-wetland areas and
uplands are generally quite obvious on aerial photos and are stark evidence to
mismanagement of the public lands. Color infrared photos exhibit the seasonal
and topographic aspects of range suitability and carrying capacity. Used in
allotment planning, aerial photos assist in planning livestock access points, pasture
design, and riparian-wetland protection.
Technical Reference 1737-6, Management Techniques in Riparian Areas (Smith
and Prichard 1992), discusses methods to achieve specific goals and objectives in
riparian-wetland management. The basic management unit for these techniques is
the watershed. Small-scale aerial photos and satellite imagery are excellent tools
for becoming familiar with a watershed. They allow a broader perspective than
on-site observation and present a more comprehensive picture than a topographic
map. Some of the management techniques that are enhanced by using aerial
photos include:
Fencing: Exclosures are areas that are easily distinguished on an aerial photo.
Aerial photos may be used to measure and determine the amount of fencing
required and to determine acreage associated with fenced areas.
Prescribed burns: Aerial photos can assist in prescribed burn planning. Topography and fuel characteristics are features easily identified from photos. Fire breaks
and control lines can be determined. Digital image processing techniques have
been used in the past to create fire fuels map products for states in the Western
U.S. These products, produced at a small scale, determine fuel type and burn
characteristics using remotely sensed satellite data.
Forestry practices: Forest management traditionally uses remote sensing techniques for planning, inventory, and monitoring.
Mineral activities: Mineral activities offer extensive opportunities to develop
areas of new riparian-wetland vegetation. Aerial photos and satellite imagery
provide the capability to detect surface disturbance as well as healthy plant vigor.
Change detection and monitoring activities in mining areas are excellent
applications for remote sensing techniques in either a digital or manual environment.
28
Structures: Physical structures are placed in watersheds to control erosion or
degradation of a site. Aerial photos assist in planning the placement of those
structures in addition to monitoring the effects of those structures in the future.
Most failures result from trying to apply a technique that worked well for one site
without realizing that the new site is different. This mistake can be avoided by
using small-scale imagery, which allows the surrounding landform, soils, and
watershed to be studied to determine the possible effectiveness of the plan.
Beaver management: Beaver can be used to naturally transform pioneer woody
vegetation into physical features that result in the expansion of floodplain, riparianwetland community structure, diversity, and productivity (Dickinson 1971).
Beaver activity is uniquely evident on aerial photos. Types of adjacent woody
vegetation can also be identified by aerial photos (Parsons and Brown 1978).
Bank stabilization: Streambank stabilization efforts are aided by the use of
historical photos for change detection purposes. Natural erosive components of
the surrounding landscape can help determine the potential of the area.
Recreation planning: In recreation planning, determining riparian-wetland
values is extremely important. The entire ecosystem should be taken into consideration. Photos can be used to develop future trail systems, plan site design to
minimize vehicular impacts to riparian-wetland areas, evaluate adjacent uplands
for potential hazards to human concentrations, and determine floodplain extent.
Road construction: Road construction planning should always incorporate the
use of aerial photos to help determine impacts to adjacent riparian-wetland areas.
Landform, vegetation inventory, flood potential, and watershed analysis are just a
few components that can be studied from an aerial perspective.
29
30
VI. Summary
Remote sensing techniques provide valuable information for riparian-wetland area
management. Aerial photos and satellite imagery can be used to establish baseline
data on which future management is based.
The first step in acquiring aerial photo baseline data is to define the objective of the
project, and to select the appropriate scale and film type to meet that objective. Then
research is conducted to determine whether photos with the desired specifications
exist.
Contracting for aerial photography is an option if appropriate photos for the area of
interest are not available. Planning for a contract involves selecting the area; determining the season, time of day to fly, and film type; and selecting the scale. Prior to
the flight, ground targets are placed to provide ground reference for determining
photo scale, and vegetation data is collected on-site for use during analysis.
Once the photos have been acquired, interpretation can be accomplished by local
BLM staff, State or NSTC personnel, or contracted photo interpreters. Interpretation
procedures consist of preparing photos, determining a minimum mapping unit
(MMU), developing a vegetation analysis framework, and analyzing photos. Photo
mensuration derived directly from the photos is possible on smaller projects or when
approximate measurements are acceptable.
If data is to be used for analysis purposes in a GIS environment, interpretations are
transferred to a stable map base from the photos. After transferring data to an
orthophoto, digitization into a GIS is possible.
Remote sensing techniques allow resource specialists to monitor an area when field
conditions do not allow on-site visits. Changes in management strategies for riparianwetland areas, which are characteristically highly responsive to modifications, are
easily monitored at specified intervals. Remotely sensed data can also be used in
determining classification, assessing functionality, and supporting other management
techniques addressed in the Riparian Area Management technical reference series.
To ensure that specific objectives are met, projects involving remote sensing must be
carefully designed and executed. The NSTC remote sensing staff is available to
provide support and assistance at each stage of the project.
31
32
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33
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in riparian areas. TR 1737-6. Bureau of Land Management, BLM/SC/PT-92/
003+1737, Denver, CO. 44 pp.
Winward, A. 2000. Monitoring the vegetation resources in riparian areas. General
Technical Report RMRS-GTR-47. U.S. Department of Agriculture, Forest Service,
Rocky Mountain Research Station, Ogden, UT. 49 pp.
34
Appendix A
Minimum Mapping Unit Templates
35
Scale
1"
1 acre
10 acres
1:40,000
1"= 3,333'
255 acres
1"
1 acre
10 acres
1:24,000
1"= 2,000'
91.8 acres
871'
50'
100'
436'
1"
1 acre
1:12,000
1"= 1,000'
10 acres
23 acres
1742'
25'
50'
100'
36
871'
436'
1"
Scale
1 acre
1:9,000
1"= 750'
12.9 acres
1742'
25'
871'
50'
100'
10 acres
436'
10 acres
1:6,000
1 acre
1"
1"= 500'
5.7 acres
1742'
25'
871'
50'
100'
436'
5 acres
1"
1:4,800
1"= 400'
1 acre
3.7 acres
1742'
25'
871'
50'
100'
436'
37
38
Appendix B
Sample Vegetation Analysis Framework
39
Riparian-Wetland Plant Community Photo Analysis Form
(can be attached on photo or overlay when complete)
Site Name
Photo Number
Date
Interpreter
Dominant Species Groups
1. Herbaceous Vegetation - Minimum Mapping Unit (MMU) is 1 acre. Herbaceous vegetation is dominant and comprises 75% or more of the ground cover.
Shrubs and trees may be present but amount to less than MMU.
1____________acres
2. Shrubs - MMU is 1 acre. Shrubs are dominant and comprise 75% or more of
canopy. Trees and herbaceous vegetation may be present but amount to less
than MMU.
2____________acres
3. Trees - MMU is 1 acre. Trees 10 feet high are dominant and comprise 75% or
more of canopy. Shrubs and herbaceous vegetation may be present but
amount to less than MMU.
3____________acres
4. Riparian-Wetland Vegetation - Scarce or absent. A linear measurement of the
length of stream where there is an absence of riparian-wetland vegetation in
MMU amounts. If less than 200 feet in length, disregard and include in other
types (dominant or mixed).
4____________acres
Mixed Communities
MMUs of mixed types are 1 acre. Tree, shrub, or herbaceous vegetation less than
75% cover with a lesser amount of one or two other groups included in a mixed
community.
5. Shrub/herbaceous vegetation
5____________acres
6. Tree/herbaceous vegetation
6____________acres
7. Tree/shrub
7____________acres
8. Tree/shrub/herbaceous vegetation
8____________acres
Total riparian-wetland
40
____________acres
Appendix C
Remote Sensing Application Guide
for Riparian-Wetland Management
41
General Comments
1) The Scale column indicates suggested scales only. Appropriate scale selection is
dependent on the size of the area under consideration. Larger or smaller scales
may be used for the applications listed, but may create more interpretive work for
the analyst. Scale selection should be carefully determined based on the area of
consideration and the intended use.
2) Scale column abbreviations represent the following:
L = Large scale (1:2,400 to 1:12,000)
M= Medium scale (1:15,840 to 1:30,000)
S = Small scale (< 1:30,000)
3) The Film Type column indicates suggested film types only. In many instances,
other film types are also appropriate for the applications listed.
4) Film Type column abbreviations represent the following:
B=
C=
I =
S=
Black and white
Natural color
False color infrared
Satellite imagery
5) The following table provides examples of various remote sensing applications that
can be used in riparian-wetland management. This list of applications is by no
means inclusive.
42
Remote Sensing Application Guide for
Riparian-Wetland Management*
Task/Application
Scale
Film
Type
S
B/I/S
Comments
Project Planning
Synoptic view
Provides an overall perspective of the area;
general condition, limiting factors, watershed delineation; ecoregion
delineation.
Linear miles
S
B/C/I
Area identification
S
B/C/I /S
Derived from descriptive scale.
Locating areas in need of further
examination; defining reaches; identifying
field inventory sites.
Geomorphology/landform
S
C
Drainage pattern
S
B
Inventory
Riparian-wetland
Slope, aspect, relief.
Technical References 1737-2**; 1737-3
M
I
Springs, seeps, wet meadow as habitat
type related to the associated vegetation.
Vegetation
Acreage determination
L
C/I
Interpretations should be transferred to an
orthophoto for map accuracy calculation.
The photo scale needed is dependent on
the size of the riparian-wetland areas to be
measured.
Density
L
I
Cottonwoods, willows.
Reproduction
L
I
Young trees, but not seedlings.
Structure
L
C
Height of vegetation.
Streambank shade
L
C
Streambank stability
L
I
Associated with vegetation composition.
Species composition
L
I
Cottonwoods, willows.
Percent cover
L
I
Trees, shrubs, herbaceous, bare soil.
Stream width
M
C
Floodplain
M
C
Streambed silt
M
I
Stream channel stability
M
C
S
C/I
Hydrology
& movement
Channel sinuosity
Photos often identify current channel
patterns better than older 7 1/2-minute
topographic maps.
43
Task/Application
Scale
Film
Type
M
B/C
Comments
Soils
Soil determination
Assists in identifying and recording soil
information.
Soil characteristics
M
B/C
Setting & associated
M
C
Slope, aspect, relief, wetness.
land features
Classification
Potential
Technical References 1737-5; 1737-7
M
B/C/I
Compare historical photography to
determine past management practices.
Limiting factors
S
C
Look at a larger area to determine
possible factors effecting riparian-wetlands
in the area of interest.
Field site planning
S
C/I
Use to identify locations for gathering
vegetation, hydrology, and soils data.
General watershed quality
S
C/I
Surface geology
S
C
Open water surface area
M
C/I
Scale depends on size of water body.
Acreage determination
L
C/I
See Inventory section.
Assessing Functionality
Provides broad perspective of watershed.
Technical References 1737-9; 1737-11;
1737-12; 1737-15; 1737-16
Planning
Existing condition
L
I
Scale is dependent on the size of the
riparian-wetland area.
Potential condition
L
I
Resource values
M
C/I
Use historical photography to assess.
Beaver dams, waterfowl habitat; evaluate
surrounding ecovalues.
M
C/I
See Management Planning section.
Monitoring
—
—
See Monitoring section.
Preliminary assessment
M
I
Management technique
planning
of functionality
Use smaller scale imagery to assess a
large area, then focus on areas that
appear to need further investigation.
44
Scale
Film
Type
Riverine/miles
S
I
General assessment.
Riverine/nonriverine acres
S
I
General assessment.
Functional condition
M
I
General indicators.
Trend
M
C/I
Task/Application
Comments
Reporting tables
General indicators using historical
photography.
Management Planning
Technical References 1737-4**; 1737-6;
1737-14
Grazing
M
C/I
Allotment planning applications.
Ecosystem-based
S
C/I
Provides a synoptic view of an area.
evaluation
Project planning
Aerial photos are important ancillary data
that should be examined prior to any
management decision.
Exclosures
M
C
Prescribed burns
M
C/I
Physical structures
M
C
Streambank stabilization
M
C
Road construction
M
C
Mineral activities
M
C
Recreation planning
M
C
Monitoring
Technical References 1737-2**; 1737-3;
1737-8** and General Technical Report 47.
All applications that are listed in the
Inventory section apply to monitoring.
Trend
—
—
Monitoring should attempt to replicate
previous scale and film type as closely as
possible.
* This table is not intended as an all-inclusive list of applications for riparian-wetland management.
** This publication is out of print. Copies may be available in libraries.
45
46
Appendix D
Aerial Photo Samples
47
Photo 1a is a portion of a natural
color aerial photo of Texas Creek,
Colorado, acquired October 14,
1976, at approximately 1:15,840
scale (i.e., 1 inch represents 1,320
feet). The arrow in the aerial shot
indicates the gravel bar and bare
ground seen in Photo 1b, which is
a ground shot of the same area.
Photo 1b depicts on-the-ground
conditions for Texas Creek in
September 1976. The gravel bar
and bare ground are obvious
indicators of a nonfunctional
stream.
Photo 1a
Photo 1b
48
Photo 2a is a portion of a color
infrared aerial photo of Texas
Creek, Colorado, acquired July 9,
1983, at approximately 1:24,000
scale (i.e., 1 inch represents
2,000 feet). The photo shows
evidence of revegetation along
the streambank, and the gravel
bars are no longer evident.
Photo 2b shows Texas Creek in
June 1978 in a functional — at
risk condition. Management
actions were changed in 1977 to
reverse the trend of Texas Creek
and allow the area to progress
towards its capability and
potential.
Photo 2a
Photo 2b
49
Photo 3a is a portion of a NAPP
color infrared aerial photo of
Texas Creek, Colorado, acquired
September 29, 1988, at approximately 1:40,000 scale (i.e., 1 inch
represents 3,333 feet). The arrow
indicates taller vegetation, as
seen in Photo 3b of the same
area, as well as a higher spectral
response from the healthy vegetation along the streambank.
Photo 3b is a ground shot of
Texas Creek in July 1987, showing the area in Properly Functioning Condition (PFC).
Photo 3a
Photo 3b
50
Photo 4
Photo 4 is an enlargement of the NAPP color infrared aerial photo (Photo 3a) of Texas
Creek, Colorado, to approximately 1:24,000 scale.
51
Photo 5
Photo 5 is a portion of a color infrared aerial photo of Muddy Creek, Wyoming, acquired
August 17, 1993, at approximately 1:3,000 scale (i.e., 1 inch represents 250 feet).
52
Photo 6a
Photo 6a is a portion of a color
infrared aerial photo of the Blackfoot
River, Idaho, acquired August 2, 1993,
at approximately 1:4,800 scale (i.e., 1
inch represents 400 feet). The arrows
indicate where ground targets (panels) are visible. Targeting should be
annotated on topographic maps,
along with distance between targets
and dominant vegetation information.
The box shown on a portion of a
1:24,000-scale topographic map (6b)
corresponds to the area shown in the
aerial photo.
6b
53
Photo 7
Photo 7 is a portion of a color infrared aerial photo of Tabor Creek, Nevada, acquired
July 16, 1984, at approximately 1:2,400 scale (i.e., 1 inch represents 200 feet).
Interpretations were compiled on clear mylar overlays registered to the fiducial marks on
the photo.
54
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4. TITLE AND SUBTITLE
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RIPARIAN AREA MANAGEMENT TR 1737-10
The Use of Aerial Photography to Manage Riparian-Wetland Areas
6. AUTHOR(S)
Pam Clemmer
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
8. PERFORMING ORGANIZATION
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U.S. Department of the Interior
Bureau of Land Management
National Science and Technology Center
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Denver, CO 80225-0047
BLM/ST/ST-01/002+1737
(formerly BLM/SC/ST-94/005+1737)
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This technical reference was originally produced as an enhanced version of RIPARIAN AREA MANAGEMENT TR 1737-2,
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published in September 1994.
12b. DISTRIBUTION CODE
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13. ABSTRACT (Maximum 200 words)
This technical reference provides basic information, concepts, and procedures associated with using
aerial photography to establish baseline data for effective management of riparian-wetland areas.
Suggestions for the use of various scales of photography, guidance for acquiring aerial photography,
and general procedures for conducting a vegetation inventory are included.
15. NUMBER OF PAGES
14. SUBJECT TERMS
• Aerial photography
• Remote sensing
• Riparian area management
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